Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?
For a zero-parameter, no-output-schema tool, the description is reasonably complete. It specifies what is listed and the information returned. However, it lacks any mention of scope (e.g., all sessions for the current workspace or user) or ordering, leaving a minor ambiguity. Still, given the simplicity, it is adequate.
Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.